Refrigerator defrosting device



' Jan. 16, 1951 I E E. H. AYERS 2,538,639

REFRIGERATOR DEFROSTING DEVICE Filed May 28, 1948 TO 64055 caumcns Invehb0?- 1 Edgar- H. A evs His Attorney Patented Jan. 16, 1951 REFRIGERATORDEFROSTING DEVICE Edgar H. Ayers, Schenectady, N. Y., assignor toGeneral Electric Company, a corporation of New York Application May 28,1948, Serial No. 29,801

7 Claims.

My invention relates to control devices, more particularly to electricrefrigerating motor control devices, and has for its object a simple andreliable arrangement providing an automatically operable defrostingcycle.

This invention is an improvement over the invention described andclaimed in Patent 2,314,240, issued to Joseph W. Owens on March 16,1943, and assigned to the same assignee as this invention.

In carrying out my invention in one form, I provide a ratchetarrangement progressively movable in response to recurrent movements ofa pressure-actuated device responsive to temperature changes. Thisdevice in turn is associated with an operating member responsive to themovement thereof to operate a switch member between open and closedcircuit positions in response to upper and lower temperature limits.Associated with the ratchet is a stop member comprising a disk having aplurality of depressions in the periphery thereof. The stop member isadapted to move in step with the ratchet and arranged to engage a membercoupled to said switch member. In the unengaged relation of the couplingmember and one of the depressions in the stop member, this member servesto limit the distance the switch can open. When the coupling memberengages one of the depressions this limiting action is removed and theswitch is opened an abnormally greater distance. As a result of thisarrangement, the operating member requires an appreciably greatermovement to close said switch member. This greater movement requires ahigher pressure in the actuating device, and so provides acorrespondingly higher temperature for defrosting.

For a more complete understanding of my invention reference should behad to the accompanying drawing in which Fig. 1 is a plan view of acontrol device embodying my invention; Fig. 2 is a sectional View alongthe line 2-2 of Fig. 1 looking in the direction of the arrows; Figs. 3,4 and 5 are diagrammatic presentations of se quential operatingmovements of the device.

Referring to the drawing, in one form of my invention I provideover-center spring snap operating means for the switching meanscomprising a pivoted switch arm or lever I3 mounted on a pivot l6 andprovided with a flexible arm I3A carrying on its end a movable contactI! which cooperates with a stationary electric contact I8. This switcharm 13 is actuated by a pivoted operating arm or lever ll having a pivotHA and operated by a temperature responsive device or bellows l2. Theover-center spring connection between these two arms H and I3 comprisesa U-shaped link IOB having its ends pivotally secured on a pivot IS onthe ends of two laterallyextending projections l9 (only one of which isshown) which are spaced apart and secured to the end of the operatingarm II. The cross or base portion of the link is connected by anovercenter helical tension spring In with a projection IOA on the end ofthe switch arm l3 and extending laterally therefrom. This projection IOAis positioned to move between the projections 19 upon relative movementbetween the two arms II and I3. Stops 40 and 4|, made ofelectrically-insulating material, are provided on opposite sides of thelink NIB adjacent its closed movable end for the purpose of limiting themovement of this end.

In the operation of this over-center snap mechanism, the determiningfactor is the relative positions of the pivot l5 and the pivot 42forming the connection between the spring [0 and the projection IllA.When the pivot J5 is below the pivot 42, as viewed in Fig. 1, the springapplies a force holding the link IDB against the upper stop 40 and aforce to the arm l3 biasing it in a counterclockwise direction so as tohold the contact I! in engagement with the contact l8. It now the arm II is raised, as viewed in Fig. 4, until the pivot I5 is slightly abovethe pivot 42, then the spring applies a component of force tending tomove the link IOB clockwise about it pivot l5 into engagement with thelower stop M. This. of course, changes the position of the end of thespring and thereby reverses its component applied to the arm l3. As seenin Fig. 4, the spring applies a force along a line passing through thepivot 42 and extending above the pivot l5. Soon after the link IOBbegins to move downward, the line of force of the spring moves below thepivot 16 whereby a counterclockwise torque is applied to the arm 13 andthe arm is therefore snapped in a counterclockwise direction to causethe contacts to assume an open circuit position.

In accordance with my invention, I provide for an abnormally greatmovement of the arm H3 in the circuit opening direction whereby thepivot 42 is allowed to move to a lower position, as seen in Fig. 5, andas a result, in order to move the contact arm l3 to its closed circuitposition the arm ll, must be moved correspondingly lower. To effectthis, a higher bellows pressure and higher temperature are required withthe result that the evaporator of the refrigerator, to the temperatureof which the bellows is responsive, is allowed to reach a highdefrosting temperature before the refrigerator motor is restarted.

In the form of my invention shown, I also provide an extension Mextending downwardly and laterally from the switch arm 13, as viewed inFig. 2. On its end this extension I4 is provided with a portion 20behind a, bellows spring adjusting screw 22, parallel therewith, andprojecting through an aperture 22A provided for it in the enclosingcasing 3| for bringing the mechanism into cooperative relation with aknob 23 secured on the end of the adjustment screw 22.

Control of the desired refrigerating temperature is accomplished byadjusting a loading spring 2| by means of the adjusting screw 22.Rotation of the knob 23 causes engagement of a projection 24 on theinner end of the knob with the downwardly-extending portion 20.

When the knob 23 is rotated in a counterclockwise direction it willcause the projection 24 to actuate the portion 20 thereby to open thecontacts I '|l8 and disable the refrigerator. Increasingly coldertemperatures are provided by rotating the knob in a clockwise direction.Normal defrosting of a refrigerator, utilizing the type of control justdescribed, is accomplished by disabling the refrigerating unit until thefrost has melted from the evaporator. This is, of course, a manualoperation and requires the personal attention of the operator.

The abnormally greater movement of the contact l'l above referred to isaccomplished in the following manner. I provide a ratchet wheel 25,having integral therewith an annular stop member 25 which has on theperiphery thereof a plurality of depressions 21. The ratchet wheel andstop member are rotatably supported on the pivot iii of the switch armH. Means for progressively moving the ratchet wheel and stop member inresponse to contractive movements of the bellows I2 is provided byengagement of the ratchet wheel with a dog or ratchet arm 28 secured tothe bellows lever or operating arm II. The dog is attachedby soldering,welding or other suitable means.

Means for controlling the movement of the contact I! during normaloperation of the refrigerator is provided by a coupling member 29pivotally mounted on a pin 30 which is secured to the case 3|. mountedso as to be balanced about a fulcrum which is disposed intermediate themiddle portion of this member and one end thereof. The last-mentionedend is provided with a lateral member 32 for engagement with thedepressions 21 in the stop member 26. Since the fulcrum of the couplingmember 23 is disposed as just described, a small movement of the lateralportion 32 will cause an appreciably greater movement of the lowerportion 33 of said member.

The portion 33 is so arranged that it comes to rest against a transverseportion 34 provided for in the member l4. This arrangement serves tolimit the movement of the switch arm l3 and its associated parts duringthe normal operation of the bellows l2 as will be presently explained.

Referring now to Fig. 3 there is illustrated, diagrammatically, theoperating position of the control device when the unit is in itsrefrigerating phase, the contacts "-13 being in a closed position. Itwill be observed that the coupling member 23 is so disposed that thelateral portion 32 thereof is now an appreciable distance from the stopmember 25.

Assuming now that the temperature in the refrigerator has reached asuitable refrigerating value, the bellows l2 will contract due to thelowered temperature and the lever H will move upwardly to cause thecontact I! to move away from its associated contact it through themediumof over-center spring arrangement. The resulting movement of theoperating arm II, as

The coupling member 23 is pivotally shown in Fig. 4, in addition tomoving the contact ll, simultaneously causes the ratchet wheel 25 tomove progressively in a counterclockwise direction and the lateralportion 32 of the coupling member to bear against the stop member 26.The last-mentioned action has a braking effect on the stop member andlimits the movement of contact carrying lever I3. The braking effectalso prevents the movement of the ratchet wheel 25 in a clockwisedirection when the bellows 12 starts its expansive movement.

In Fig. 5, the stop member 26 has been progressively rotated in themanner above-described until one of the depressions 21 engages thelateral portion 32 of the coupling member 23. In this position of thecoupling member, the contact I! has moved an abnormalv distance awayfrom the contact l8 and as a result the bellows I: will now have toexpand over a greater distance in order to trip the over-center springarrangement which controls the movement of the contact arm l3. Thisrequirement of added expansion of the bellows l2 creates a demand for anincrease of temperature in the refrigerator. In the process ofexpanding, the bellows l2 gradually forces the lever or operating arm llagainst an auxiliary load spring 35 which further augments the increasein temperature and the load which the bellows must overcome before thetripping action of the over-center spring arrangement can take place.The load member 35 is made ad justable by the provision of threadedmember 36 in threaded engagement with the case 3|, the unthreaded end ofthe member being terminated in a flange 31, the size of which is adaptedto accommodate the load member 35.

When it is desirable at any time during the aforementioned automaticdefrosting cycle, il-

lustrated in Fig. 5, to place the unit in operation for refrigerating, Iprovide by means of the projection 24 on the inner side of the knob 23,independent means for closing the contacts lll8. This I do by rotatingthe knob 23 in a clockwise direction until a projection 33 on theperiphery of the knob abuts a stop 33 on the case 3|. In this positionthe projection 24 now urges the lateral portion 20 to the left, withrespect to the drawing, therebyto move the contact I! into closedcircuit relation with the contact I! through the medium of the lever l3.

The embodiment of my invention which I have described and illustratedwas selected for the purpose of setting forth the principles involved.It will be obvious that the invention may be modilied to meet variousconditions and it is, therefore, intended to cover by the appendedclaims all such modifications which fall within the spirit and scope ofmy invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a refrigerator control device, a pivoted overcenter switch lever,a pivoted temperature responsive operating lever coupled to actuate saidswitch lever overcenter and movable recurrently between spaced-apartswitch opening and switch closing positions at which such actuationtakes place, said switch opening and switch closing positions defininglower and upper temperature limits respectively, a freely movable stopmember associated with said switch lever to determine said switchclosing position of said operating lever, said stop member normallybeing positioned to determine a first switch closing position defining anormal upper temperature limit, and means progressively movable byrecurrent movement of said operating lever for recurrently positioningsaid stop member to determine a second switch closing position beyondsaid first switch closing position, thereby to define an abnormally highupper temperature limit.

2. In a refrigerator control device, a pivoted overcenter switch lever,a pivoted temperature responsive operating lever, a spring memberconnected to couple said levers and bias said switch lever to either ofa pair of spaced-apart open and closed positions, said open and closedpositions defining lower and upper temperature limits respectively, afreely movable stop member asso- V ciated with said switch lever fordetermining said open position, said stop member normally beingpositioned to determine a first open position defining a normal uppertemperature limit, and means progressively movable by recurrent movementof said operating lever while said switch lever is in said closedposition and said stop disengaged for recurrently positioning said stopmember to determine a second open position defining an abnormally highupper temperature limit.

3. In a refrigeratorcontrol device, a temperature responsive member, alever directly actuated by said temperature responsive member, a pivotedsnap action overcenter switch arm coupled to I said lever and actuablethereby between spacedapart open and closed positions, said open andclosed positions defining upper and lower temperature limitsrespectively, a freely movable stop member associated with said snapaction switch arm for determining said open position, said stop membernormally being positioned to determine a first open position defining anormal upper temperature limit, and means progressively movable byrecurrent movement of said lever while said switch arm is in said closedposition and said stop disengaged for recurrently positioning said stopmember to determine a second open position of said switch arm definingan abnormal upper temperature limit.

4. In a refrigerator control device, a pivoted overcenter switch arm, apivoted temperature responsive operating arm coupled to actuate saidswitch arm overcenter and movable recurrently between spaced-apartswitch opening and switch closing positions, said switchopening andswitch closing position defining lower and upper temperature limitsrespectively, a freely rotatable annular stop member associated withsaid switch arm to determine a first switch closing position defining anormal upper temperature limit, said stop member being provided with atleast one depression in the periphery thereof to determine a secondswitch closing position defining an abnormally high upper temperaturelimit, and means progressively movable by recurrent movement of saidoperating arm for rotating said stop member while it is disengaged,retractive reverse movement of said operating arm occurring while saidswitch arm is in said open position and said stop member engaged andheld.

5. In a refrigerator control device, a movable temperature responsivemember, a lever directly actuated by said temperature responsive member,a snap action overcenter switch arm coupled to said lever and actuablethereby recurrently between spaced-apart open and closed positions, saidopen and closed positions defining switch opening and switch closingpositions of said lever and corresponding lower and upper temperaturelimits respectively of said temperature responsive member, a freelyrotatable annular stop member disposed 'to limit movement of said switcharm and thereby to determine a first switch closing lever position and acorresponding normal upper temperature limit, said stop member beingprovided with at least one depression in the periphery thereof todetermine a second switch closing lever position and acorresponding'abnormal upper temperature limit, and means progressivelymovable by recurrent switch opening movement of said lever to rotatesaid stop member and position said depression to define said secondswitch closing position.

6. In a refrigerator control device, the combination of a pivotedovercenter switch arm, a temperature responsive pivoted operating arm, aspring operatively connected between said arms and arranged to bias saidswitch arm overcenter to spaced-apart open and closed circuit position,a freely rotatable stop member arranged to determine the open circuitposition of said switch arm, a progressively movable member actuated byswitch opening movement of said operating arm for recurrently movingsaid stop member to an abnormal position upon completion of apredetermined number of movements of said operating arm thereby toprovide for an abnormal open circuit position of said switch arm wherebyan increased movement of said operating arm is required to move saidswitch arm to its closed circuit position, and resilient means in thepath of movement of said operating arm for resisting the increasedmovement thereof .thereby to require an'increased temperature to actuatesaid operating arm to move said switch arm to its closed circuitposition.

'7. In a refrigerator defrosting device, a movable temperatureresponsive operating member, a first lever pivotally mounted and coupledto be moved directly by said operating member, a pair of contacts, asecond pivotally mounted lever coupled 'to said first lever forovercenter actuation by said first lever and arranged to support one ofsaid contacts for movement relative to the other contact, a ratchetmember freely rotatably supported on the pivot of said second lever,means mounted upon said first lever for progressively moving saidratchet member in response to recurrent switch opening movements of saidoperating member, an annular stop member connected to said ratchetmember and arranged normally to determine the open circuit position ofsaid second lever, said stop member having a depression in theperipherythereof providing for abnormal switch opening movement of saidsecond lever, and a member pivotally mounted to engage said stop memberand saidsecond lever, thereby to couple said stop to determine the opencircuit position of said second lever and to release said stop memberfor free advancing movement upon recurrent switch opening actuatingmovement of said operating member.

EDGAR H. AYERS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,833,544 Vold Nov. 24, 19311,914,055 Vold June 13, 1933 1,933,580 Bauer Nov. 7, 1933 1,944,084 HuttJan. 16, 1934

